CRT Supply Dropping Out
See function block K of A6 Power Supply Schematic Diagram in the Component-Level
Information binder.
The CRT Supply is a separate switching supply which provides the
Vdc for the
Al7 CRT Driver from a winding on the
HV Module. The CRT Supply operates at
approximately 30
The exact frequency is determined by the inductance of the primary
winding of
and
The supply will only operate if the HV-SHUT-DOWN line
is high.
If the power supply keeps dropping out, there is probably a short on the Al7 CRT Driver
assembly.
1. Disconnect W8 from
2. Connect an IC clip to
and connect a jumper between
pin 10 and TP308
Vdc).
3. Connect a voltmeter to TP405 and set the (LINE) switch on.
4. Check TP405 for a voltage of approximately
Vdc. It will probably measure higher
since there is no load on the supply.
5. If the voltage at TP405 is correct, suspect a short on A17. If the voltage at TP405 is not
correct, check pin
pin 8 for a sawtooth signal. The sawtooth should be flat-topped
and about 5 Vp-p at a frequency of about 30
6. If the sawtooth is not flat-topped, suspect
and its associated circuitry.
7. If the sawtooth is correct, check the base of Q401 for 30
pulses.
8. If the duty cycle is high, but there is no
Vdc, suspect the bridge rectifier, CR401
through CR404.
Blanking Signal
1. Connect an oscilloscope probe to A25202 pin 3. Connect the oscilloscope ground lead to
TP3. Set the oscilloscope to the following settings:
Sweep Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vertical Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
2. If a 4 Vp-p signal is not observed, the A2 Controller Assembly is faulty.
3. Repeat steps 1 and 2 with the oscilloscope probe on A25202 pin 14.
4. Set the oscilloscope to the following settings:
Sweep Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vertical Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
5. Connect the positive probe lead to A2J202 pin 15. This is the blanking output.
6. TTL-level pulses should be observed. If the signal is either always high or always low, the
display will be blanked; suspect the A2 Controller Assembly.
7. If the signals on A2J202 pins 3, 14, and 15 are correct, troubleshoot the Al7 CRT Driver.
Display/Power Supply Section 12-15
Содержание 8560A
Страница 93: ......
Страница 150: ... ...
Страница 178: ...4 20 Replaceable Parts ...
Страница 180: ...4 22 Replaceable Parts ...
Страница 182: ...4 24 Replaceable Parts ...
Страница 184: ...4 26 Replaceable Parts ...
Страница 186: ...4 28 Replaceable Parts ...
Страница 188: ...4 30 Replaceable Parts ...
Страница 190: ...4 32 Replaceable Parts ...
Страница 191: ......
Страница 192: ......
Страница 193: ......
Страница 194: ......
Страница 195: ......
Страница 200: ...w 5 4 A 4 w 5 5 W 2 7 Figure 5 3 Top View A2 and A3 Unfolded SK157 Major Assembly and Cable Locations 5 5 ...
Страница 205: ...Bl Figure 5 8 Rear View BTl A20 5 10 Major Assembly and Cable Locations ...
Страница 249: ...6 44 General Troubleshooting ...
Страница 250: ......
Страница 251: ......
Страница 252: ......
Страница 253: ......
Страница 282: ......
Страница 307: ......
Страница 319: ......
Страница 324: ...8 42 IF Section ...
Страница 325: ......
Страница 326: ......
Страница 327: ......
Страница 344: ......
Страница 397: ......
Страница 398: ......
Страница 423: ......
Страница 441: ...12 18 Display Power Supply Section ...
Страница 442: ......
Страница 443: ......
Страница 449: ...A 6 Component Level Information Packets ...
Страница 450: ......